Apparatus and method for shipping and storing volatile hydrocarbons



LATILE HYDROCARBONS Nov. 30, 1951 L. MORRISON ND METHOD FOR SHIPPING ANDSTORING V0 W. APPARATUS A Filed April 5, 1955 Z1200? Z01" Zfiz Wardl Jfr/zis a)? 4% W m fii/arzzqys United States Patent APPARATUS AND METHODFOR SHIPPING AND STORING VOLATILE HYDROCARBONS Willard L. Morrison, LakeForest, 111., assignor to Union Stock Yards & Transit Company, Chicago,Ill., a corporation of Illinois Application November 30, 1951, SerialNo. 259,253 11 Claims. (Cl. 62-123) My invention relates to apparatusand method for lilquefying volatile hydrocarbons such as natural gas andt e l' e.

One object of my invention is to use the pressure of the gas as it flowsfrom the well to assist in providing the power required to cool andliquefy such gas.

Another object of my invention is to use some of the gas as fuel toprovide the remaining power needed for the refrigeration andliquefaction of the gas.

Another object of my invention is to utilize both the natural pressureof the gas as it is discharged from the well and the fuel value of someof the gas to provide the power to refrigerate and liquefy the gas sothat it may be stored or shipped as a cold liquid at substantiallyatmosphere pressure.

The pressure at which gas is discharged from a natural gas well variesin different parts of the country and with respect to diflferent wellsthrough a wide range of difference. However, in most instances thepressure is many hundreds of pounds, frequently several thousand poundsabove atmospheric and it is this excess of pressure above atmosphericwhich makes it possible to use the gas as a motive fluid to furnish partof the power required.

My invention is especially applicable to those wells which produce drygas and I have illustrated my invention as applied to a situation wherethe dry gas without intermediate treatment between the well and myapparatus furnishes a motive fluid to drive a turbine and also some ofit furnishes fuel to add the additional power required to compress,refrigerate and liquefy the dry gas from the well. Of course, myinvention could be used under other circumstances where wet gas wasproduced or where some treatment of the gas took place between the welland my liquefaction apparatus.

Assuming, for example, that I apply my method to a well wherein the gasis discharged at approximately 1500 pounds gauge pressure through a pipewhich discharges gas to my apparatus at that pressure and at 80 degreesF. I propose first to cool this gas down to approximately 40 degrees F.

This initial cooling will be accomplished by refrigerating machinerywherein the evaporator includes a heat exchanger through which the gaspasses to be reduced from 80 degrees F. to 40 degrees F.

I propose thereafter to further reduce the temperature of the gas fromsaid -40 to say -80 degrees F. and to discharge such gas as a motivefluid into a turbo-expander where work will be done, the motive fluidbeing discharged from the turbo-expander at substantially atmosphericpressure and at temperature down to as low as 258 degrees F.

The exhaust from the turbo-expander at the pressure and temperatureabove referred to will be a wet gas wherein approximately seventypercent by weight of the gas will be dry and approximately thirtypercent by weight of the gas will be a liquid.

This wet gas will be discharged to a separator or to a gas-tightreceiver wherein the liquid gas will be separated from the dry gas andretained or stored. The dry gas still at approximately 258 degrees F.will then pass through a heat exchanger which is interposed between theinitial cooling point above referred to and the turboexpander and it isthis remaining dry gas which will be utilized to lower the temperatureof the gas from 40 to -80 degrees F.

This dry gas, the temperature of which has been raised as a result ofits passage through the heat exchanger, will then be compressed back tothe temperature and pressure of the original gas and will be joined withsuch gas for recycling, the process continuing as long as new gas issupplied from the well to the system in such an amount as to replace inthe system the gas withdrawn by liquefaction.

The additional power required beyond that generated by the motive fluidpassing through the turbo-expander will be provided by the combustion ofsome of the gas in any suitable form of power generating mechanism suchas an internal combustion turbine, internal combustion engine or byburning the gas as fuel under a boiler, the fuel value of the gas beingsuch that only a relatively small part of the gas need be burned togenerate sufficient power to carry out the refrigeration andliquefaction cycle.

My invention is illustrated diagrammatically in the accompanying drawingwhich shows in part elevation and part section an apparatus to carry outmy invention.

Like parts are indicated by like characters throughout the specificationand drawing.

1 is a duct which will be supplied with natural gas at well or casinghead pressure from the well, or may be supplied with gas from any othersuitable source. 2 is a duct in continuation of duct 1 of somewhatlarger section leading to the cooler 3. The pipe 8 in the cooler 3 isthe evaporator of a refrigerating machine which includes a compressor 4,a condenser 5, and pipes 6, 7, 9, joining them in closed circuit. 10 isa duct leading from the cooler 3 to the heat exchanger 11. 12 is a ductleading from the heat exchanger 11 to the turbine 13 where work is doneby the gas under pressure and where the gas is expanded and cooled todischarge through the duct 14. The wet gas resulting is led to theseparator 15 where the liquid is separated from the dry gas and may bedischarged through the duct 16 to any suitable reservoir.

The dry gas passes through the duct 17, cooling coil 18 in the heatexchanger 11, and duct 19 to the compressor 20. The gas enters thecompressor 20 at substantially atmospheric pressure, its temperaturehaving been raised by its passage through the heat exchanger 11.

21 is the duct leading from the compressor 20 to the duct 2, the ducts2, 10, and 12 being of larger cross section than the ducts 1, 17, 19 and21 to accommodate the values of the recirculating dry gas. Thecompressor 20 raises the pressure and temperature of the gas toapproximately that of the gas discharged from the well.

22 is a prime mover. 23 is a duct leading from the compressor 20 to theprime mover 22. The prime mover may take the form of an internalcombustion engine, an internal combustion turbine or even a boiler underwhich gas is burned to generate steam to operate the engine. The detailsof this prime mover form no part of the present invention. Sufiice it tosay that some of the dry gas is supplied to the prime mover for thepurpose of providing the additional power required to operate thesystem. 24 is a drive shaft connecting the prime mover 22, the turbine 3and the compressors 20 and 4 whereby some of the power to operate thecompressors is furnished by the turbine and some of the power isfurnished by the prime mover.

The temperatures and pressures referred to above are entirelyillustrative. The gas discharged from the well is at natural casing heatpressure or at any other pressure desired, circulates through the systemwhere the high pressure gas is cooled, and does work. This results inthe liquefaction of some of the gas which will remain as a liquid insuspension in the dry gas and the resulting moisture is what I refer toas wet gas. I propose to extract the liquid from the wet gas and thatgives me a resulting dry gas at low temperature and low pressure. Thiscold dry gas provides some of the cooling effect to cool the gascirculated in the system before it reaches the work center orturbo-expander and insures the discharge from the turbine or work centerof a wet gas. The gas now heated to some extent passes through thecompressor where it is further heated and brought back up to thepressure and temperature of the gas entering the system. It thenrecirculates through the system with the new gas brought in to replacethe gas extracted from the system by the separating out of the liquefiedgas.

Cooling the gas will, to some extent, reduce its pressure as itcirculates toward the turbine, the amount of temperature and pressurechange in a matter of design depending on circumstances. At thedischarge end of the system, the pressure must be substantiallyatmospheric and the temperature must be low enough so that some of thegas liquefies. At the intake end of the system, the pressure of therecirculated gas must be the same as the pressure of the gas enteringthe system from the outside, though no harm will be done if thetemperature of the recirculated gas varies somewhat from the temperatureof the new gas. The two pressures must balance, the temperatures mayvary within reason.

25 is a valve to control the flow of fresh gas to the system, it may bemanually or automatically operated, as desired.

I claim:

1. The method of liquifying natural gas for shipment and storage, whichconsists in discharging raw gas from a well at casing head pressure,cooling it by heat exchange with a refrigerating coolant, in a separateclosed circuit, expanding the cooled raw gas in a work zone withresultant further reduction of temperature and liquefaction of some ofthe gas, recovering the liquified gas, using the cold stripped gas toadditionally cool the raw gas on its way to the work zone, thencompressing the stripped gas to the pressure of the raw gas mixing ittherewith and recirculating the stripped and the raw gas for furtherexpansion and liquefaction.

2. The method of liquifying natural gas for shipment and storage, whichconsists in discharging raw gas from a well at casing head pressure,expanding the raw gas in a work zone with resultant reduction intemperature and liquefaction of some of the gas, using the cold strippedgas to cool the raw gas on its way to the work zone, then compressingthe stripped gas to the pressure of the raw gas, mixing it therewith andrecirculating the stripped and raw gas from the well for furtherexpansion and liquefaction.

3. The method of liquifying natural gas for shipment and storage, whichconsists in discharging raw gas from a well at casing head pressure,cooling it by heat exchange with a refrigerating coolant, in a separateclosed circuit, expanding the cooled raw gas in a work zone withresultant further reduction of temperature and liquefaction of some ofthe gas, recovering the liquified gas, using the cold stripped gas toadditionally cool the raw gas on its way to the work zone, thencompressing the stripped gas to the pressure of the raw gas mixing ittherewith and recirculating the stripped and the raw gas for furtherexpansion and liquefaction burning some of the gas, using the powergenerated in the work zone and the power resulting from burning some ofthe gas to provide the power necessary to compress the stripped gas andto cool and circulate the refrigerating coolant.

4. The method of liquefying natural gas for shipment and storage, whichconsists in discharging raw gas from awell at casing head pressure,expanding the raw gas in a work zone with resultant reduction intemperature and liquefaction of some of the gas, using the cold strippedgas to cool the raw gas on its way to a work zone, then compressing thestripped gas to the pressure of the raw gas, mixing it therewith andrecirculating the stripped and raw gas from the well for furtherexpansion and liquefaction burning some of the gas, using the powergenerated in the work zone and the power resulting from burning some ofthe gas to provide the power necessary to compress the stripped gas.

5. The method of liquifying natural gas for shipment and storage, whichconsists in discharging raw gas from a well at casing head pressure,expanding the raw gas in a work zone with resultant reduction intemperature and liquefaction of some of the gas, using the cold strippedgas to cool the raw gas on its way to the work zone, then compressingthe stripped gas to the pressure of the raw gas, mixing it therewith andrecirculating the stripped and raw gas from the well for furtherexpansion and liquefaction, while continuing the circulation andrecirculation of the raw and stripped gas without discharge in gaseousform from the system.

6. In means for liquifying natural gas for shipment and storage, acontinuous closed circuit, means for supplying natural gas thereto froma well at casing head pressure, the circuit including in series aturbine where the raw gas under pressure does work, is expanded, cooledand in part liquified, a separator adapted to recover the liquified gas,a heat exchanger where the stripped cold gas cools the raw gas on itswayto the turbine, a compressor adapted to raise the pressure of thestripped gas back to the pressure at which the raw gas enters thecircuit, means for mixing the raw and the stripped gas and means forcontrolling the rate of supply of raw gas to compensate for the removalof liquified gas from the circuit.

7. In means for liquifying natural gas for shipment and storage, acontinuous closed circuit, means for supplying natural gas thereto froma well at casing head pressure, the circuit including in series aturbine where the raw gas under pressure does work, is expanded, cooledand in part liquified, a separator adapted to recover the liquified gas,a heat exchanger where the stripped cold gas cools the raw gas on itsway to the turbine, a compressor adapted to raise the pressure of thestripped gas back to the pressure at which the raw gas enters thecircuit, means for mixing the raw and the stripped gas and means forcontrolling the rate of supply of raw gas to compensate for the removalof liquefied gas from the circuit, separate means independent of thetemperature of the circulating gas for additionally cooling the gasbefore it reaches the turbine.

8. In means for liquifying natural gas for shipment and storage, acontinuous closed circuit, means for supplying natural gas thereto froma well at casing head pressure, the circuit in series includes a turbinewhere the raw gas under pressure does work, is expanded, cooled and inpart liquified, a separator adapted to recover the liquified gas, a heatexchanger where the stripped cold gas cools the raw gas on its way tothe turbine, a compressor adapted to raise the pressure of the strippedgas back to the pressure at which the raw gas enters the circuit, meansfor mixing the raw and the stripped gas and means for controlling therate of supply of raw gas to compensate for the removal of liquified gasfrom the circuit, a prime mover, means for supplying gas for combustiontherein and power transmission means between the prime mover, theturbine and compressor whereby the turbine and the prime mover furnishthe power necessary to operate the compressor.

9. In means for liquifying natural gas for shipment and storage, acontinuous closed circuit, means for supplying raw natural gas to saidcircuit from a well at natural casing head pressure, the circuitincluding an expander turbine where the raw gas under pressure doeswork, is expanded, cooled and in part liquified, a separator adapted tostrip the gas and discharge the liquid from the circuit, a heatexchanger where the stripped cold gas cools the raw gas on its way tothe turbine, a compressor adapted to raise the pressure of the strippedgas to the pressure at which the raw gas enters the CllClllt, to assistin recirculating the gas through the clrcuit, means for controlling therate of supply of gas to the circuit to compensate for the liquified gasdischarged from the circuit.

10, In means for'liquifying natural gas for shipment and storage, acontinuous closed circuit, means for supplying raw natural gas to saidcircuit from a well at natural casing head pressure, the circuitincluding an expander turbine where the raw gas under pressure doeswork, is expanded, cooled, and in part liquified, a separator adapted tostrip the gas and discharge the liquid from the circuit, a heatexchanger where the stripped cold gas cools the raw gas on its way tothe turbine, a compressor adapted to raise the pressure of the strippedgas to the pressure at which the raw gas enters the circuit, to assistin recirculating the gas through the circuit, means for controlling therate of supply of gas to the .circuit to compensate for the liquifiedgas discharged from the circuit, separate means independent of the gasin the circuit for additionally cooling the gas before it reaches theturbine.

11. In means for liquifying natural gas for shipment and storage, acontinuous closed circuit, means for supplying raw natural gas to saidcircuit from a well at natural casing head pressure, the circuitincluding an expander turbine where the raw gas under pressure doeswork, is expanded, cooled and in part liquified, a

separator adapted to strip the gas and discharge the liquid from thecircuit, a heat exchanger where the stripped cold gas cools the raw gason its way to the turbine, a compressor adapted to raise the pressure ofthe stripped gas to the pressure at which the raw gas enters thecircuit, to assist in recirculating the gas through the circuit, meansfor controlling the rate of supply of gas to the circuit to compensatefor the liquified gas discharged from the circuit, separate meansindependent of the gas in the circuit for additionally cooling the gasbefore it reaches the turbine, a prime mover means for supplying gas toit for combustion therein for the generation of power and powertransmission means between the prime mover and the turbine and thecompressor whereby they together furnish the power necessary to operatethe compressor.

References Cited in the file of this patent UNITED STATES PATENTS StrongNov. 4, Bottoms Mar. 22, Schlumbohm June 8, Weil Dec. 7, Vaughan Oct.18, Zerkowitz July 11, Moore July 30, De Baufre et a1. Apr. 29,Harrington May 20,

Keith Aug. 8, Gay Jan. 6, Laverty Mar. 7, Hughes Sept. 19, Bodle June19, Deming June 24,

Kapitza Aug. 26,

1. THE METHOD OF LIQUIFYING NATURAL GAS FOR SHIPMENT AND STORAGE, WHICHCONSISTS IN DISCHARGING RAW GAS FORM A WELL AT CASING HEAD PRESSUE,COOLING IT BY HEAT EXCHANGE WITH A REFRIGERATING COOLANT, IN A SEPARATECLOSED CIRCUIT, EXPANDING THE COOLED RAW GAS IN A WORK ZONE WITHRESULTANT FURTHER REDUCTION OF TEMPERATURE AND LIQUEFACTION OF SOME OFTHE GAS, RECOVERING THE LIQUIFIED GAS,